2.1 DJ ISCU Fault. repair/replacement

[Eamless]

Hello,
I've had a recurring and intermittent problem which now manifests itself as a variable idle when the van is at running temp and very rough running at certain rpm/load conditions (to the point where it pulled the AFM off the rubber boot on a couple of occasions) normal running otherwise. Have replaced several parts: temp 2, coil, ignition unit. Spent much time setting throttle stop and switch. cleaned ISV which has always buzzed nicely.

Took ISCU out and had a peak at the board. What looks like a large green spiral wound resistor, which resides at the top end of the fixed board, has bad heat damage to the point that I can only read 5......0% on the component. The rest of the boards look nice and shiney.

So does anyone know of/have circuit details for the ISCU or know exactly what the component is so I can try another?
this is a little bit of a long shot and there is the possibility of unseen damage
so is there anywhere in Britain (have seen gowesty and vanagain) I can get a new/rebuilt ISCU to try/buy?

Can I just confirm that the throttle stop screw on an 88 dj is set at contact plus 1/2 a turn as I've seen different things probably because of the use of the digifant type single microswitch replacing the use of 2 separate switches on top.

Any advice gratefully received,
thanks
Eamless